Dual cure additive manufacturing resins for production of flame retardant objects

ABSTRACT

The present invention concerns methods of forming a three-dimensional object, and polymerizable liquids such as dual cure resins useful for making a three-dimensional object by sterolithography, such as by continuous liquid interface production (CLIP), wherein the three-dimensional object is flame retardant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.17/271,360, filed Feb. 25, 2021, which is a 35 U.S.C. § 371 nationalphase application of International Application Serial No.PCT/US2019/049913, filed Sep. 6, 2019, which claims the benefit of U.S.Provisional Application Ser. No. 62/729,118, filed Sep. 10, 2018, theentire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention concerns polymerizable liquids, polymercompositions formed therefrom, and methods of making such polymercompositions, preferably in the form of shaped three-dimensional objectsby additive manufacturing techniques such as continuous liquid interfaceproduction.

BACKGROUND OF THE INVENTION

In conventional additive or three-dimensional fabrication techniques,construction of a three-dimensional object is performed in a step-wiseor layer-by-layer manner. Typically, layer formation is performedthrough solidification of photo curable resin under the action ofvisible or UV light irradiation. Generally referred to as“stereolithography,” two particular techniques are known: one in whichnew layers are formed at the top surface of the growing object; theother in which new layers are formed at the bottom surface of thegrowing object. Examples of such methods include those given in U.S.Pat. No. 5,236,637 to Hull (see, e.g., FIGS. 3-4), U.S. Pat. Nos.5,391,072 and 5,529,473 to Lawton, U.S. Pat. No. 7,438,846 to John, U.S.Pat. No. 7,892,474 to Shkolnik, U.S. Pat. No. 8,110,135 to El-Siblani,U.S. Patent Application Publication No. 2013/0292862 to Joyce, and USPatent Application Publication No. 2013/0295212 to Chen et al.

Recently, techniques referred to as “continuous liquid interfaceproduction” (or “CLIP”) have been developed. These techniques enable therapid production of three-dimensional objects in a layerless manner, bywhich the parts may have desirable structural and mechanical properties.See, e.g., J. DeSimone et al., U.S. Pat. Nos. 9,211,678, 9,205,601,9,216,546, J. Tumbleston, et al., Continuous liquid interface productionof 3D Objects, Science 347, 1349-1352 (2015), and R. Janusziewcz et al.,Layerless fabrication with continuous liquid interface production, Proc.Natl. Acad. Sci. USA 113, 11703-11708 (2016).

More recently, dual cure stereolithography resins suitable forstereolithography techniques (particularly for CLIP) are described in J.Rolland et al., U.S. Pat. No. 9,453,142, and US Patent ApplicationPublication Nos. US 2016/0136889, US 2016/0137838 and US 2016/016077.These resins usually include a first polymerizable system typicallypolymerized by light (sometimes referred to as “Part A”) from which anintermediate object is produced, and also include at least a secondpolymerizable system (“Part B”) which is usually cured after theintermediate object is first formed, and which impart desirablestructural and/or tensile properties to the final object.

These two developments have spurred the application of additivemanufacturing processes beyond the manufacture of (primarily) prototypeobjects, to functional objects more suited to a variety of end uses.

SUMMARY OF THE INVENTION

Provided herein according to some embodiments is a method of forming athree-dimensional object, comprising: (a) providing a polymerizableliquid comprising a mixture of (i) a light polymerizable firstcomponent, (ii) a second solidifiable component that is different fromsaid first component, wherein said second solidifiable componentcomprises flame retardant groups (e.g., halogen groups such as bromine,e.g., in an amount of from 1, 2, or 5% to 15 or 20% by weight of thepolymerizable liquid), and (iii) optionally, a flame retardant synergist(e.g., an antimony or aromatic amine synergist, e.g., in an amount offrom 0.1, 0.5 or 1% to 3, 4, or 5% by weight of the polymerizableliquid); (b) producing a three-dimensional intermediate from saidpolymerizable liquid by an additive manufacturing process includingirradiating said polymerizable liquid with light to form a solid polymerscaffold from said first component and containing said secondsolidifiable component carried in said scaffold in unsolidified and/oruncured form, said intermediate having the same shape as, or a shape tobe imparted to, said three-dimensional object; optionally wherein saidpolymerizable liquid further comprises an organic diluent and whereinsaid irradiating is performed under conditions in which said organicdiluent chemically reacts (e.g., degrades, isomerizes, cross-reacts, orpolymerizes (e.g., with a light polymerizable component), etc.) by anamount sufficient to increase the strength of said intermediate; (c)optionally washing said intermediate, and (d) concurrently with orsubsequent to said producing step (b), further curing said secondsolidifiable component in said three-dimensional intermediate to formsaid three-dimensional object.

In some embodiments, the polymerizable liquid comprises a toughener(e.g., a core-shell rubber, a thermoplastic toughener, etc., includingcombinations thereof), preferably in an amount of from about 5 or 10 to20, 25 or 30 percent by weight, and optionally wherein the toughener hasa phenol, amine, epoxide, or isocyante reactive end group that isreactive with epoxides.

In some embodiments, the producing step (b) is carried out bystereolithography (e.g., bottom-up stereolithography such as continuousliquid interface production).

In some embodiments, the producing step (b) is carried out by: (i)providing a carrier and an optically transparent member having a buildsurface, said carrier and said build surface defining a build regiontherebetween; (ii) filling said build region with said polymerizableliquid, and (iii) irradiating said build region with light through saidoptically transparent member to form said solid polymer scaffold fromsaid first component and also advancing said carrier and said buildsurface away from one another to form said three-dimensionalintermediate.

In some embodiments, the further curing step (d) is carried outsubsequent to said producing step (b), and optionally but preferablysubsequent to said washing step (c).

In some embodiments, the further curing step (d) is carried out byheating, microwave irradiating, or both heating and microwaveirradiating.

In some embodiments, the polymerizable liquid comprises: (a)light-polymerizable monomers and/or prepolymers that can participate informing an intermediate object by stereolithography (preferably includedin an amount of from 5, 10, or 20 percent by weight to 50, 60, or 80percent by weight); and (b) heat-polymerizable monomers and/orprepolymers (preferably included in an amount of from 5, 10 or 20percent by weight to 40, 50 or 60 percent by weight); optionally, but insome embodiments preferably, wherein the light polymerizable monomersand/or prepolymers comprise reactive end groups selected from the groupconsisting of acrylates, methacrylates, α-olefins, N-vinyls,acrylamides, methacrylamides, styrenics, epoxides, thiols, 1,3-dienes,vinyl halides, acrylonitriles, vinyl esters, maleimides, and vinylethers; and/or optionally, but in some embodiments preferably, whereinthe heat polymerizable monomers and/or prepolymers comprise reactive endgroups selected from the group consisting of: epoxy/amine,epoxy/hydroxyl, oxetane/amine, oxetane/alcohol, isocyanate/hydroxyl,isocyanate/amine, isocyanate/carboxylic acid, cyanate ester,anhydride/amine, amine/carboxylic acid, amine/ester, hydroxyl/carboxylicacid, hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H,Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde, amine/aldehyde,hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast, alkyne/azide,click chemistry reactive groups, alkene/sulfur, alkene/thiol,alkyne/thiol, hydroxyl/halide, isocyanate/water, Si—OH/hydroxyl,Si—OH/water, Si—OH/Si—H, Si—OH/Si—OH, perfluorovinyl, diene/dienophiles,olefin metathesis polymerization groups, olefin polymerization groupsfor Ziegler-Natta catalysis, and ring-opening polymerization groups andmixtures thereof.

In some embodiments, the polymerizable liquid further comprises ahardener (e.g., included in an amount of at least 1, 5, or 10 percent byweight, up to 40 or 50 percent by weight) (e.g., the hardener comprisinga compound having amine, thiol, vinyl ether, maleimide, or allylreactive end groups).

In some embodiments, the polymerizable liquid further comprises at leastone photoinitiator (e.g., in an amount of from 0.1 to 1 or 5 percent byweight), optionally at least one dye (e.g., in an amount of 0.001 or0.01 to 1 or 5 percent by weight), and optionally at least one filler(e.g., in an amount of 0.01 or 0.1 to 20 or 50 percent by weight).

In some embodiments, the second solidifiable component comprises anepoxy or cyanate ester resin, preferably in an amount from 20 or 30percent by weight to 50, 60 or 70 percent by weight.

In some embodiments, the second solidifiable component comprises anepoxy (e.g., a brominated epoxy), optionally in combination with acyanate ester resin.

In some embodiments, the organic diluent comprisesN,N′-dimethylacrylamide, n-vinyl-2-pyrrolidone, n-vinyl formamide,n-vinyl caprolactam, acryloylmorpholine, or a combination of two or morethereof.

In some embodiments, the polymerizable liquid comprises a hardener(e.g., an amine hardener such as a diaminodiphenyl sulfone hardener),optionally, but preferably, with said organic diluent included in anamount sufficient to dissolve said hardener in said polymerizableliquid.

In some embodiments, the polymerizable liquid comprises a chain extender(e.g., a dihydric phenolic compound) (e.g., in an amount of from 5 or 10to 20, 25 or 30 percent by weight), and optionally further comprises achain extender catalyst (e.g., an onium salt such as a phosphonium salt)(e.g., in an amount of from 0.01, 0.05 or 0.1 to 2, 5 or 10 percent byweight).

In some embodiments, the flame retardant synergist is present andcomprises an antimony synergist (e.g., antimony pentoxide such asantimony pentoxide functionalized with ethoxylated amine).

In some embodiments, the three-dimensional object is rigid.

Also provided herein is a polymer blend comprising a light polymerizedfirst component and a heat polymerized second component, wherein samplesof the polymer blend configured for testing according to UL 94 andhaving a thickness of 2 millimeters achieve a UL 94 V-0, V-1, or V-2rating (e.g., achieves a UL 94 V-0 rating).

In some embodiments, the polymer blend has a notched Izod ImpactStrength of at least 30, 40, or 50 J/m when measured in accordance withASTM D256, and/or a heat deflection temperature of at least 80, 90, or100 degrees Centigrade when measured in accordance with ASTM D648.

In some embodiments, the polymer blend comprises a toughener (e.g., acore-shell rubber, a thermoplastic toughener, etc.), preferably in anamount of from about 5 or 10 percent by weight to 20, 25 or 30 percentby weight.

In some embodiments, the heat polymerized second component comprises anepoxy or cyanate ester polymer, preferably in an amount from 20 or 30percent by weight to 50, 60 or 70 percent by weight.

In some embodiments, the heat polymerized second component comprises anepoxy polymer (e.g., a brominated epoxy polymer), optionally incombination with a cyanate ester polymer.

In some embodiments, the polymer blend is configured as athree-dimensional object, said object produced by the process ofadditive manufacturing (e.g., stereolithography, such as continuousliquid interface production).

Further provided herein is a dual cure resin useful for making athree-dimensional object by stereolithography, comprising: (a)light-polymerizable monomers and/or prepolymers that can participate informing an intermediate object by stereolithography such as CLIP (e.g.,included in an amount of from 1, 5, or 10 percent by weight, to 50, 60,or 80 percent by weight); (b) heat-polymerizable monomers and/orprepolymers (e.g., included in an amount of from 5 or 10 percent byweight to 50 or 60 percent by weight); (c) a hardener (e.g., a compoundhaving amine, thiol, vinyl ether, maleimide, or allyl reactive endgroups) (e.g., included in an amount of at least 1, 5, or 10 percent byweight, up to 40 or 50 percent by weight), or a chain extender (e.g., adihydric phenolic compound) (e.g., in an amount of from 5 or 10 to 20,25 or 30 percent by weight) (and optionally further comprising a chainextender catalyst (e.g., an onium salt such as a phosphonium salt)(e.g., in an amount of from 0.01, 0.05 or 0.1 to 2, 5 or 10 percent byweight)); (d) optionally, a flame retardant synergist (e.g., an antimonyor aromatic amine synergist, e.g., in an amount of from 0.1, 0.5 or 1%to 3, 4, or 5% by weight of the polmyerizable liquid); and (e)optionally, an organic diluent in a viscosity-reducing effective amount,optionally, but preferably, wherein said diluent solubilizes ordissolves said hardener in said resin, wherein one or both of said: (a)heat-polymerizable monomers and/or prepolymers, and said (c) hardener orchain extender, comprises flame retardant groups (e.g., halogen groupssuch as bromine, e.g., in an amount of from 1, 2, or 5% to 15 or 20% byweight of the resin).

In some embodiments, the resin may further include: (f) a toughener(e.g., a core-shell rubber, a thermoplastic toughener, etc., includingcombinations thereof), preferably in an amount of from about 5 or 10 to20, 25 or 30 percent by weight, optionally wherein the toughener has aphenol, amine, epoxide, or isocyante reactive end group that is reactivewith epoxides.

In some embodiments, the hardener comprises a polyamine (e.g., a diaminehardener such as a diaminodiphenyl sulfone hardener), optionally, butpreferably, with said organic diluent included in an amount sufficientto dissolve said hardener in said resin.

In some embodiments, the resin comprises both of said hardener and saidchain extender.

In some embodiments, the diluent comprises N,N′-dimethylacrylamide,n-vinyl-2-pyrrolidone, n-vinyl formamide, n-vinyl caprolactam,acryloylmorpholine, or a mixture of two or more thereof.

In some embodiments, the light polymerizable monomers and/or prepolymerscomprise reactive end groups selected from the group consisting ofacrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

In some embodiments, the heat polymerizable monomers and/or prepolymerscomprise reactive end groups selected from the group consisting of:epoxy/amine, epoxy/hydroxyl, oxetane/amine, oxetane/alcohol,isocyanate/hydroxyl, isocyanate/amine, isocyanate/carboxylic acid,cyanate ester, anhydride/amine, amine/carboxylic acid, amine/ester,hydroxyl/carboxylic acid, hydroxyl/acid chloride, amine/acid chloride,vinyl/Si—H, Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde,amine/aldehyde, hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast,alkyne/azide, click chemistry reactive groups, alkene/sulfur,alkene/thiol, alkyne/thiol, hydroxyl/halide, isocyanate/water,Si—OH/hydroxyl, Si—OH/water, Si—OH/Si—H, Si—OH/Si—OH, perfluorovinyl,diene/dienophiles, olefin metathesis polymerization groups, olefinpolymerization groups for Ziegler-Natta catalysis, and ring-openingpolymerization groups and mixtures thereof.

In some embodiments, the resin further comprises at least onephotoinitiator (e.g., in an amount of from 0.1 to 1 or 5 percent byweight), optionally at least one dye (e.g., in an amount of 0.001 or0.01 to 1 or 5 percent by weight), and optionally at least one filler(e.g., in an amount of 0.01 or 0.1 to 20 or 50 percent by weight).

In some embodiments, the resin comprises a cyanate ester or epoxy resin.

In some embodiments, the resin comprises an epoxy (e.g., a brominatedepoxy), optionally in combination with a cyanate ester resin.

Still further provided herein is a method of making a three-dimensionalobject, comprising: (a) providing a dual cure resin as taught herein;(b) producing by additive manufacturing a three-dimensional intermediatefrom said dual cure resin, said intermediate having the same shape as,or a shape to be imparted to, said three-dimensional object, saidadditive manufacturing including irradiating the resin with light; (c)optionally washing said intermediate; and then (d) heating saidintermediate (i.e., to a temperature at which said heat-polymerizablemonomers and/or prepolymers polymerize) to produce saidthree-dimensional object.

In some embodiments, the irradiating is carried out under conditions inwhich said organic diluent chemically reacts (e.g., degrades,isomerizes, cross-reacts, and/or polymerizes (e.g., with a lightpolymerizable component), etc.) by an amount sufficient to increase thestrength of said intermediate.

In some embodiments, the light polymerizable monomers and/or prepolymersform a solid polymer scaffold during said stereolithography step (b),which scaffold degrades during said heating step (d) and forms aconstituent necessary for the polymerization of said heat polymerizablemonomers and/or prepolymers.

In some embodiments, the producing step (b) is carried out bystereolithography (e.g., bottom-up stereolithography).

In some embodiments, the producing step (b) is carried out by continuousliquid interface production.

Still further provided is a three-dimensional object produced by amethod or resin as taught herein, wherein samples of the compositionthat are configured for testing according to UL 94 and have a thicknessof 2 millimeters achieve a UL 94 V-0 rating.

The foregoing and other objects and aspects of the present invention areexplained in greater detail in the drawings herein and the specificationset forth below. The disclosures of all United States patent referencescited herein are to be incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents the schematic of a setup for a UL94V Verital BurningTest of a specimen for classification according to V1, V1 or V2, withthe Test Criteria of afterflame time of specimen/drip of flamingparticles. In all of these burning tests, an open flame is applied for aspecified time to the specimen. As the burning behavior also depends onthe thickness of the material, the thickness of the specimen should beindicated.

FIG. 2 presents a graph of instability index for four different resinformulations. As shown in the data, the BurnEx® ADP Part B-2 formulationis more stable as compared to the Nyacol APE 1540 Part B-1 formulation.This lower instability index promotes a longer shelf life of theproduct.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is now described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein; rather these embodiments are provided sothat this disclosure will be thorough and complete and will fully conveythe scope of the invention to those skilled in the art.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

“Shape to be imparted to” refers to the case where the shape of theintermediate object slightly changes between formation thereof andforming the subsequent three-dimensional product, typically by shrinkage(e.g., up to 1, 2 or 4 percent by volume), expansion (e.g., up to 1, 2or 4 percent by volume), removal of support structures, or byintervening forming steps (e.g., intentional bending, stretching,drilling, grinding, cutting, polishing, or other intentional formingafter formation of the intermediate product, but before formation of thesubsequent three-dimensional product).

1. Resins.

Dual cure polymerizable liquids (or “resins”) useful in additivemanufacturing, particularly for stereolithography techniques such ascontinuous liquid interface production (CLIP) are known and describedin, for example, J. Rolland et al., U.S. Pat. Nos. 9,453,142, 9,598,606,9,676,963, and US 2016/01600077. In general, such resins can comprise:(a) light-polymerizable monomers and/or prepolymers that can form anintermediate object (typically in the presence of a photocatalyst); and(b) heat-polymerizable (or otherwise further polymerizable) monomersand/or prepolymers.

A. Light-polymerizable monomers and/or prepolymers. Sometimes alsoreferred to as “Part A” of the resin, these are monomers and/orprepolymers that can be polymerized by exposure to actinic radiation orlight. This resin can have a functionality of 2 or higher (though aresin with a functionality of 1 can also be used when the polymer doesnot dissolve in its monomer). A purpose of Part A is to “lock” the shapeof the object being formed or create a scaffold for the one or moreadditional components (e.g., Part B). Importantly, Part A is present ator above the minimum quantity needed to maintain the shape of the objectbeing formed after the initial solidification during photolithography.In some embodiments, this amount corresponds to less than ten, twenty,or thirty percent by weight of the total resin (polymerizable liquid)composition.

Examples of suitable reactive end groups suitable for Part Aconstituents, monomers, or prepolymers include, but are not limited to:acrylates, methacrylates, α-olefins, N-vinyls, acrylamides,methacrylamides, styrenics, epoxides, thiols, 1,3-dienes, vinyl halides,acrylonitriles, vinyl esters, maleimides, and vinyl ethers.

An aspect of the solidification of Part A is that it provides a scaffoldin which a second reactive resin component, termed “Part B,” cansolidify during a second step, as discussed further below.

B. Heat-polymerizable monomers and/or prepolymers. Sometimes alsoreferred to as “Part B”, these constituents may comprise, consist of orconsist essentially of a mix of monomers and/or prepolymers that possessreactive end groups that participate in a second solidification reactionduring or after the Part A solidification reaction. In general, for dualcure resins, examples of methods used to solidify Part B include, butare not limited to, contacting the object or scaffold to heat, water orwater vapor, light at a different wavelength than that at which Part Ais cured, catalysts, (with or without additional heat), evaporation of asolvent from the polymerizable liquid (e.g., using heat, vacuum, or acombination thereof), microwave irradiation, etc., includingcombinations thereof. In some embodiments, heat curing of the “Part B”resins is preferred.

Examples of suitable reactive end group pairs suitable for Part Bconstituents, monomers or prepolymers include, but are not limited to:epoxy/amine, epoxy/hydroxyl, oxetane/amine, oxetane/alcohol,isocyanate*/hydroxyl, isocyanate*/amine, isocyanate/carboxylic acid,anhydride/amine, amine/carboxylic acid, amine/ester, hydroxyl/carboxylicacid, hydroxyl/acid chloride, amine/acid chloride, vinyl/Si—H(hydrosilylation), Si—Cl/hydroxyl, Si—Cl/amine, hydroxyl/aldehyde,amine/aldehyde, hydroxymethyl or alkoxymethyl amide/alcohol, aminoplast,alkyne/azide (also known as one embodiment of “Click Chemistry,” alongwith additional reactions including thiolene, Michael additions,Diels-Alder reactions, nucleophilic substitution reactions, etc.),alkene/sulfur (polybutadiene vulcanization), alkene/peroxide,alkene/thiol, alkyne/thiol, hydroxyl/halide, isocyanate*/water(polyurethane foams), Si—OH/hydroxyl, Si—OH/water, Si—OH/Si—H (tincatalyzed silicone), Si—OH/Si—OH (tin catalyzed silicone),perfluorovinyl (coupling to form perfluorocyclobutane), etc., whereisocyanate* includes protected isocyanates (e.g. oximes)),diene/dienophiles for Diels-Alder reactions, olefin metathesispolymerization, olefin polymerization using Ziegler-Natta catalysis,ring-opening polymerization (including ring-opening olefin metathesispolymerization, lactams, lactones, siloxanes, epoxides, cyclic ethers,imines, cyclic acetals, etc.), etc. As will be noted from the above, the“Part B” components generally comprise at least a pair of compounds thatare reactive with one another (e.g., a polyisocyanate, and a polyamine).

In some embodiments, the heat polymerizable component comprises an epoxypolymer or resin. In some embodiments, the heat polymerizable componentcomprises a cyanate ester polymer or resin. See WO 2017/040883 and WO2017/044381 to Carbon, Inc.

Example epoxy resins include, but are not limited to, a bisphenol Aepoxy resin, a bisphenol F epoxy resin, a novolac epoxy resin, analiphatic epoxy resin, a glycidylamine epoxy resin, or a combinationthereof. Numerous examples of suitable epoxy resins (and organichardeners, as described further below) are known. See, e.g., U.S. Pat.Nos. 3,945,972; 3,947,3951 4,833,226; 5,319,004; 6,355,763; 6,881,813;8,383,025; 9,133,301; etc.

In some embodiments, the epoxy resin comprises an epoxidized vegetableoil. In general, epoxidized vegetable oils can be obtained by theepoxidation of triglycerides of unsaturated fatty acids. They are madeby epoxidizing the reactive olefin groups of the naturally occurringtriglyceride oils. The olefin groups can be epoxidized with peracids,such as perbenzoic, peracetic and the like, and with hydrogen peroxide.Suitable epoxidized vegetable oils are epoxidized linseed oil,epoxidized soybean oil, epoxidized corn oil, epoxidized cottonseed oil,epoxidized perilla oil, epoxidized safflower oil, etc. See, e.g., U.S.Pat. Nos. 3,051,671; 5,973,082; 8,481,622; and 9,169,386; see also M.Stemmelen et al., A fully biobased epoxy resin from vegetable oils: Fromthe synthesis of the precursors by thiol-ene reaction to the study ofthe final material, J. Polym Sci. Part A: Polym Chem. 49, 2434-2444(2011).

In some embodiments, the epoxy resin comprises a catalyzed epoxy resin(which may not require a hardener). In such case, the resin may furtherinclude an epoxy homopolymerization catalyst, such as a tertiary amineor imidizole (anionic polymerization) or boron trifluoride (cationicpolymerizations).

Example cyanate esters include, but are not limited to, 1,3-, or1,4-dicyanatobenzene; 1,3,5-tricyanatobenzene; 1,3-, 1,4-, 1,6-, 1,8-,2,6- or 2,7-dicyanatonaphthalene; 1,3,6-tricyanatoaphthalene; 2,2′ or4,4′-dicyanatobiphenyl; bis(4-cyanathophenyl) methane;2,2-bis(4-cyanatophenyl) propane;2,2-bis(3,5-dichloro-4-cyanatophenyl)propane,2,2-bis(3-dibromo-4-dicyanatophenyl)propane; bis(4-cyanatophenyl)ether;bis(4-cyanatophenyl)thioether; bis(4-cyanatophenyl) sulfone;tris(4-cyanatophenyl)phosphite; tris(4-cyanatophenyl)phosphate;bis(3-chloro-4-cyanatophenyl)methane; 4-cyanatobiphenyl;4-cumylcyanatobenzene; 2-tert-butyl-1,4-dicyanatobenzene;2,4-dimethyl-1,3-dicyanatobenzene; 2,5-di-tert-butyl-1,4dicyanatobenzene; tetramethyl-1,4-dicyanatobenzene;4-chloro-1,3-dicyanatobenzene; 3,3′,5,5′-tetramethyl-4,4′dicyanatodiphenylbis(3-chloro-4-cyanatophenyl)methane;1,1,1-tris(4-cyanatophenyl)ethane; 1,1-bis(4-cyanatophenyl)ethane;2,2-bis(3,5-dichloro-4-cyanatophenyl)propane; 2,2-bis(3,5dibromo-4-cyanatophenyl)propane; bis(p-cyanophenoxyphenoxy)benzene;di(4-cyanatophenyl)ketone; cyanated novolacs produced by reacting anovolac with cyanogen halide; cyanated bisphenol polycarbonate oligomersproduced by reacting a bisphenol polycarbonate oligomer with cyanogenhalide; mixtures thereof. See also U.S. Pat. No. 4,371,689.

In some embodiments, Part B may comprise an epoxy resin in combinationwith a cyanate ester resin.

In some embodiments, Part B constituents include a flame retardantgroup. For example, in some embodiments the constituents may bebrominated, i.e., contain one, two, three, four or more bromine groups(—Br) covalently coupled thereto. In some embodiments, the resincomposition contains additional components with the flame retardantgroups (e.g., with total bromine groups in an amount of from 1, 2, or 5%to 15 or 20% by weight of the polymerizable liquid).

In some embodiments, Part B constituents include epoxy components withflame retardant groups (e.g., brominated epoxy resin). Particularexamples include, but are not limited to, a brominated bisphenol resin,such as a brominated bisphenol A epoxy resin, a brominated bisphenol Bepoxy resin, a brominated bisphenol E epoxy resin, a brominatedbisphenol F epoxy resin, etc., or a combination of two or more thereof.In some embodiments, an oligomeric epoxy component may be used/included(e.g., a brominated epoxy oligomer such as a brominated polybisphenol Aepoxy). See, e.g., U.S. Pat. No. 10,227,482 to Arechederra, U.S. Pat.No. 10,100,190 to Shimozawa et al., U.S. Pat. No. 9,193,858 to Su etal., U.S. Pat. No. 8,991,321 to Bar-Yaakov et al., and U.S. Pat. No.5,912,308 to Das et al., which are incorporated by reference herein.

C. Additional resin ingredients. Photoinitiators included in thepolymerizable liquid (resin) can be any suitable photoinitiator,including type I and type II photoinitiators and including commonly usedUV photoinitiators, examples of which include, but are not limited to,acetophenones (diethoxyacetophenone for example), phosphine oxidesdiphenyl(2,4,6-trimethylbenzoyl)phosphine oxide,phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (PPO), Irgacure 369,etc. See, e.g., U.S. Pat. No. 9,453,142 to Rolland et al.

The liquid resin or polymerizable material can have solid particlessuspended or dispersed therein. Any suitable solid particle can be used,depending upon the end product being fabricated. The particles can bemetallic, organic/polymeric, inorganic, or composites or mixturesthereof. The particles can be nonconductive, semi-conductive, orconductive (including metallic and non-metallic or polymer conductors);and the particles can be magnetic, ferromagnetic, paramagnetic, ornonmagnetic. The particles can be of any suitable shape, includingspherical, elliptical, cylindrical, etc. The particles can be of anysuitable size (for example, ranging from 1 nm to 20 μm averagediameter).

The particles can comprise an active agent or detectable compound asdescribed below, though these may also be provided dissolved orsolubilized in the liquid resin as also discussed below. For example,magnetic or paramagnetic particles or nanoparticles can be employed.

The liquid resin can have additional ingredients solubilized therein,including pigments, dyes, active compounds or pharmaceutical compounds,detectable compounds (e.g., fluorescent, phosphorescent, radioactive),etc., again depending upon the particular purpose of the product beingfabricated. Examples of such additional ingredients include, but are notlimited to, proteins, peptides, nucleic acids (DNA, RNA) such as siRNA,sugars, small organic compounds (drugs and drug-like compounds), etc.,including combinations thereof.

Hardeners. Any suitable hardener may be used as an additional component(see, e.g., U.S. Pat. Nos. 5,599,856; 6,656,979; 8,632,654; and9,315,698). In some embodiments, the hardener can react with an epoxide.In some embodiments, the hardener comprises an amine or polyamine (e.g.,an aromatic amine or polyamine, a cycloaliphatic amine or polyamine, analiphatic amine or polyamine such as a polyether amine, etc.).

In some embodiments, the hardener comprises a thiol or polythiol, anallyl or polyallyl (diallyls, triallyls); a maleimide; a vinyl ether,etc.

Particular examples of suitable thiol hardeners include, but are notlimited to, 4,4′-dimercaptodiphenylether, 4,4′-dimercaptobiphenyl,trimethylolpropane tris(3-mercaptopropionate), pentaerythritoltetrakis(3-mercaptopropionate),1,3,5-tris(3-mercaptopropyl)-1,3,5-triazine-2,4,6-trione, etc.

Examples of suitable allyls include, but are not limited to, allyl(meth)acrylate, 2,2′-diallylbisphenol A andtriallyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione.

In some embodiments, the hardener comprises a latent hardener (includingmixtures thereof); that is, a hardener having a low reactivity at lowertemperatures, and/or which is sparingly soluble at lower temperatures,such that the hardener can be more stable at room temperature, but thenactivated upon heating. Numerous examples of latent hardeners are known(See, e.g., U.S. Pat. No. 8,779,036; see also U.S. Pat. No. 4,859,761).Particular examples include, but are not limited to, substitutedguanidines and aromatic amines, such as dicyandiamide, benzoguanamine,o-tolylbiguanidine, bis(4-aminophenyl) sulfone (also known as diaminodiphenylsulfone: DDS), bis(3-aminophenyl) sulfone,4,4′-methylenediamine, 4-aminobenzenesulfonamide, 1,2- or 1,3- or1,4-benzenediamines, bis(4-aminophenyl)-1,4-diisopropylbenzene (e.g.,EPON 1061 from Shell),bis(4-amino-3,5-dimethylphenyl)-1,4-diisopropylbenzene (e.g., EPON 1062from Shell), bis(aminophenyl) ether, diaminobenzophenones,2,6-diaminopyridine, 2,4-toluenediamine, diaminodiphenylpropanes,1,5-diaminonaphthalene, xylenediamines,1,1-bis-4-aminophenylcyclohexane, methylenebis(2,6-diethylaniline)(e.g., LONZACURE® M-DEA from Lonza),methylenebis(2-isopropyl-6-methylaniline) (e.g. LONZACURE® M-MIPA fromLonza), methylenebis(2,6-diisopropylaniline) (e.g., LONZACURE® M-DIPAfrom Lonza), 4-aminodiphenylamine, diethyltoluenediamine,phenyl-4,6-diaminotriazine, and lauryl-4,6-diaminotriazine. Still otherexamples include N-acylimidazoles such as1-(2′,4′,6′-trimethylbenzoyl)-2-phenylimidazole or1-benzoyl-2-isopropylimidazole (see, e.g., U.S. Pat. Nos. 4,436,892 and4,587,311); Cyanoacetyl compounds such as neopentyl glycolbiscyanoacetate, N-isobutylcyanoacetamide, 1,6-hexamethylenebiscyanoacetate or 1,4-cyclohexanedimethanol biscyanoacetate (see, e.g.,U.S. Pat. No. 4,283,520); N-cyanoacylamide compounds such asN,N′-dicyanoadipic diamide (see, e.g., U.S. Pat. Nos. 4,529,821,4,550,203, and 4,618,712; acylthiopropylphenols (see, e.g., U.S. Pat.No. 4,694,096) and the urea derivatives such astoluene-2,4-bis(N,N-dimethylcarbamide) (see, e.g., U.S. Pat. No.3,386,955); and aliphatic or cycloaliphatic diamines and polyamines ifthey are sufficiently unreactive. An example which may be mentioned hereis polyetheramines, e.g., JEFFAMINE® 230 and 400. Aliphatic orcycloaliphatic diamines or polyamines whose reactivity has been reducedby steric and/or electronic influencing factors or/and are sparinglysoluble or have a high melting point, e.g., JEFFLINK® 754 (Huntsman) orCLEARLINK® 1000 (Dorf Ketal) can also be used.

Chain extenders. In some embodiments, chain extenders may include thosethat can react with epoxides to grow linear chains. Particular examplesinclude, but are not limited to, dihydric phenolic compounds such asbisphenol A, bisphenol S (4,4′-sulfonyldiphenol), bisphenol K, etc. SeeU.S. Pat. No. 4,594,219 to Berthram et al. In some embodiments, chainextenders may include a flame retardant group. For example, in someembodiments the chain extenders may be brominated, i.e., contain one,two, three, four or more bromine groups covalently coupled to the chainextenders. A non-limiting example of a brominated chain extender istetrabromobisphenol A.

Chain extender catalysts. In some embodiments, chain extender catalystsmay include those that catalyze or promote the reaction of dihydricphenolic chain extenders with epoxides to grow linear chains. Examplesof chain extender catalysts include, but are not limited to, oniumsalts, preferably phosphonium salts, and even more preferablyphosphonium halides (e.g., tetrabutylphosphonium bromide, ethyltriphenylphosphonium iodide, etc.). See U.S. Pat. Nos. 4,767,832;4,352,918; and 3,477,990, which are incorporated herein by reference. Insome embodiments, the amount of the catalyst used may be from 0.01 to 10percent, preferably from 0.05 to 5 percent, or from 0.1 to 2 percent, byweight of the composition.

Dyes/non-reactive light absorbers. In some embodiments, polymerizableliquids for carrying out the present invention include a non-reactivepigment or dye that absorbs light, particularly UV light. Suitableexamples of such light absorbers include, but are not limited to: (i)titanium dioxide (e.g., included in an amount of from 0.05 or 0.1 to 1or 5 percent by weight), (ii) carbon black (e.g., included in an amountof from 0.05 or 0.1 to 1 or 5 percent by weight), and/or (iii) anorganic ultraviolet light absorber such as a hydroxybenzophenone,hydroxyphenylbenzotriazole, oxanilide, benzophenone, thioxanthone,hydroxypenyltriazine, and/or benzotriazole ultraviolet light absorber(e.g., Mayzo BLS® 1326) (e.g., included in an amount of 0.001 or 0.005to 1, 2 or 4 percent by weight). Examples of suitable organicultraviolet light absorbers include, but are not limited to, thosedescribed in U.S. Pat. Nos. 3,213,058; 6,916,867; 7,157,586; and 7,695,643, which are incorporated herein by reference.

Fillers. Any suitable filler may be used in connection with the presentinvention, depending on the properties desired in the part or object tobe made. Thus, fillers may be solid or liquid, organic or inorganic, andmay include reactive and non-reactive rubbers, siloxanes,acrylonitrile-butadiene rubbers, reactive and non-reactivethermoplastics (including but not limited to: poly(ether imides),maleimide-styrene terpolymers, polyarylates, polysulfones andpolyethersulfones, etc.) inorganic fillers such as silicates (such astalc, clays, silica, mica), glass, carbon nanotubes, graphene, cellulosenanocrystals, etc., including combinations of all of the foregoing.Suitable fillers include tougheners, such as core-shell rubbers, asdiscussed below.

Tougheners. One or more polymeric and/or inorganic tougheners can beused as a filler in the present invention. The toughener may beuniformly distributed in the form of particles in the cured product. Theparticles could be less than 5 microns (μm) in diameter. Such toughenersinclude, but are not limited to, those formed from elastomers, branchedpolymers, hyperbranched polymers, dendrimers, rubbery polymers, rubberycopolymers, block copolymers, core-shell particles, oxides or inorganicmaterials such as clay, polyhedral oligomeric silsesquioxanes (POSS),carbonaceous materials (e.g., carbon black, carbon nanotubes, carbonnanofibers, fullerenes), ceramics and silicon carbides, with or withoutsurface modification or functionalization.

Core-shell rubbers. Core-shell rubbers are particulate materials(particles) having a rubbery core. Such materials are known anddescribed in, for example, US Patent Application Publication No.20150184039, as well as US Patent Application Publication No.20150240113, and U.S. Pat. Nos. 6,861,475, 7,625,977, 7,642,316,8,088,245, and elsewhere. In some embodiments, the core-shell rubberparticles are nanoparticles (i.e., having an average particle size ofless than 1000 nanometers (nm)). Generally, the average particle size ofthe core-shell rubber nanoparticles is less than 500 nm, e.g., less than300 nm, less than 200 nm, less than 100 nm, or even less than 50 nm.Typically, such particles are spherical, so the particle size is thediameter; however, if the particles are not spherical, the particle sizeis defined as the longest dimension of the particle. Suitable core-shellrubbers include, but are not limited to, those sold by KanekaCorporation under the designation Kaneka Kane Ace, including the KanekaKane Ace 15 and 120 series of products, including Kaneka Kane Ace MX120, Kaneka Kane Ace MX 136, Kaneka Kane Ace MX 137, Kaneka Kane Ace MX153, Kaneka Kane Ace MX 154, Kaneka Kane Ace MX 156, Kaneka Kane AceMX170, Kaneka Kane Ace MX 257 and Kaneka Kane Ace MX 120 core-shellrubber dispersions, and mixtures thereof, and those sold by Dow underthe designation Paraloid™.

Organic diluents. Diluents for use in the present invention arepreferably reactive organic diluents; that is, diluents that willdegrade, isomerize, cross-react, or polymerize, with themselves or alight polymerizable component, during the additive manufacturing step.In general, the diluent(s) are included in an amount sufficient toreduce the viscosity of the polymerizable liquid or resin (e.g., to notmore than 6,000, 5,000, 4,000, or 3,000 centipoise at 25 degreesCentigrade. Suitable examples of diluents include, but are not limitedto, N,N′-dimethylacrylamide, n-vinyl-2-pyrrolidone, n-vinyl formamide,n-vinyl caprolactam, acryloylmorpholine, and mixtures of two or morethereof. The diluent may be included in the polymerizable liquid in anysuitable amount, typically from 1, 5 or 10 percent by weight, up toabout 30 or 40 percent by weight, or more.

Flame retardant oligomers. Flame retardant oligomers, which may bereactive or non-reactive, may also be included in the resins of thepresent invention. Examples include, but are not limited to, brominatedoligomers such as ICL Flame Retardant F-3100, F-3020, F-2400, F-2016,etc. (ICL Industrial Products). See also U.S. 2013/0032375 to Pierre etal.

Flame retardant synergists. Flame retardant synergists, which whencombined with halogens such as bromine synergize flame retardantproperties, are known. Examples include, but are not limited to,antimony synergists such as antimony oxides (e.g., antimony trioxide,antimony pentaoxide, etc.), aromatic amines such as melamine, etc. SeeU.S. Pat. No. 9,782,947. In some embodiments, the resin composition maycontain synergists in an amount of from 0.1, 0.5 or 1% to 3, 4, or 5% byweight. In some embodiments, an antimony pentoxide functionalized withtriethanolamine or ethoxylated amine may be used, which is available asBurnEX® colloidal additives such as BurnEX® A1582, BurnEX® ADP480, andBurnEX® ADP494 (Nyacol® Nano Technologies, Ashland, Massachussetts).

Smoke suppression agents. The resins described herein may optionallycontain a smoke suppression agent. Such smoke suppression agents mayinclude, but are not limited to, molybdenum oxides, including MoO₃,ammonium octamolybdate (AOM), calcium and zinc molybdates; iron, copper,manganese, cobalt or vanadyl phthalocyanines, which may be used assynergist with octabromobiphenyl; ferrocenes (organometallic iron),which may be used in combination with Cl paraffin and/or antimony oxide;hydrated Iron (III) oxide; hydrated zinc borates; zinc stannate and zinchydroxy stannate; hydrates, carbonates and borates; alumina trihydrate(ATH); magnesium hydroxide; metal halides of iron, zinc, titanium,copper, nickel, cobalt, tin, aluminum, antimony and cadmium, which arenon-hydrous and non-ionic, and which may be used with complexing agentssuch as quaternary ammonium compounds, quaternary phosphonium compounds,tertiary sulfonium compounds, organic orthosilicates, the partiallyhydrolyzed derivatives of organic orthosilicates, or a combinationincluding one or more of them; nitrogen compounds, including ammoniumpolyphosphates (monammonium phosphate, diammonium phosphate, and thelike); and FeOOH. Such smoke suppression agents may be used singly or incombination, optionally in amounts of about 0.1 to about 20 wt. % of theresin composition or by weight of the polymer resins in the compositionor, in some cases, about 1 to about 5 wt. % by weight of the compositionor by weight of the polymer resins. See US 2009/0306258 to Siripurapu etal.

2. Methods of Making.

Polymerizable liquids or resins as described herein are used to makethree-dimensional objects in a first “light” cure (typically by additivemanufacturing) which generates a “green” intermediate object, followedby a second cure of that intermediate object.

Techniques for additive manufacturing are known. Suitable techniquesinclude bottom-up or top-down additive manufacturing, generally known asstereolithography. Such methods are known and described in, for example,U.S. Pat. No. 5,236,637 to Hull, U.S. Pat. Nos. 5,391,072 and 5,529,473to Lawton, U.S. Pat. No. 7,438,846 to John, U.S. Pat. No. 7,892,474 toShkolnik, U.S. Pat. No. 8,110,135 to El-Siblani, U.S. Patent ApplicationPublication Nos. 2013/0292862 to Joyce, and US Patent ApplicationPublication No. 2013/0295212 to Chen et al. The disclosures of thesepatents and applications are incorporated by reference herein in theirentireties.

In some embodiments, the intermediate object is formed by continuousliquid interface production (CLIP). CLIP is known and described in, forexample, U.S. Pat. Nos. 9,211,678, 9,205,601, 9,216,546, and in J.Tumbleston, D. Shirvanyants, N. Ermoshkin et al., Continuous liquidinterface production of 3D Objects, Science 347, 1349-1352 (2015). Seealso R. Janusziewcz et al., Layerless fabrication with continuous liquidinterface production, Proc. Natl. Acad. Sci. USA 113, 11703-11708(2016). In some embodiments, CLIP employs features of a bottom-upthree-dimensional fabrication as described above, but the irradiatingand/or said advancing steps are carried out while also concurrentlymaintaining a stable or persistent liquid interface between the growingobject and the build surface or window, such as by: (i) continuouslymaintaining a dead zone of polymerizable liquid in contact with saidbuild surface, and (ii) continuously maintaining a gradient ofpolymerization zone (such as an active surface) between the dead zoneand the solid polymer and in contact with each thereof, the gradient ofpolymerization zone comprising the first component in partially-curedform. In some embodiments of CLIP, the optically transparent membercomprises a semipermeable member (e.g., a fluoropolymer), and thecontinuously maintaining a dead zone is carried out by feeding aninhibitor of polymerization through the optically transparent member,thereby creating a gradient of inhibitor in the dead zone and optionallyin at least a portion of the gradient of polymerization zone. Otherapproaches for carrying out CLIP that can be used in the presentinvention and potentially obviate the need for a semipermeable “window”or window structure include utilizing a liquid interface comprising animmiscible liquid (see L. Robeson et al., WO 2015/164234), generatingoxygen as an inhibitor by electrolysis (see I. Craven et al., WO2016/133759), and incorporating magnetically positionable particles towhich the photoactivator is coupled into the polymerizable liquid (seeJ. Rolland, WO 2016/145182).

Other examples of methods and apparatus for carrying out particularembodiments of CLIP include, but are not limited to, those described inB. Feller, US Patent App. Pub. No. US 2018/0243976 (published Aug. 30,2018); M. Panzer and J. Tumbleston, US Patent App Pub. No. US2018/0126630 (published May 10, 2018); K. Willis and B. Adzima, USPatent App Pub. No. US 2018/0290374 (Oct. 11, 2018); Batchelder et al.,Continuous liquid interface production system with viscosity pump, USPatent Application Pub. No. US 2017/0129169; Sun and Lichkus,Three-dimensional fabricating system for rapidly producing objects, USPatent Application Pub. No. US 2016/0288376; Willis et al., 3d printadhesion reduction during cure process, US Patent Application Pub. No.US 2015/0360419; Lin et al., Intelligent 3d printing throughoptimization of 3d print parameters, US Patent Application Pub. No. US2015/0331402; and D. Castanon, Stereolithography System, US PatentApplication Pub. No. US 2017/0129167.

After the intermediate three-dimensional object is formed, it isoptionally washed, optionally dried (e.g., air dried) and/or rinsed (inany sequence). It is then further cured, preferably by heating (althoughfurther curing may in some embodiments be concurrent with the firstcure, or may be by different mechanisms such as contacting to water, asdescribed in U.S. Pat. No. 9,453,142 to Rolland et al.).

Heating may be active heating (e.g., in an oven, such as an electric,gas, solar oven or microwave oven, or combination thereof), or passiveheating (e.g., at ambient (room) temperature). Active heating willgenerally be more rapid than passive heating and in some embodiments ispreferred, but passive heating—such as simply maintaining theintermediate at ambient temperature for a sufficient time to effectfurther cure—is in some embodiments preferred.

In some embodiments, the heating step is carried out at at least a first(oven) temperature and a second (oven) temperature, with the firsttemperature greater than ambient temperature, the second temperaturegreater than the first temperature, and the second temperature less than300° C. (e.g., with ramped or step-wise increases between ambienttemperature and the first temperature, and/or between the firsttemperature and the second temperature).

For example, the intermediate may be heated in a stepwise manner at afirst temperature of about 70° C. to about 150° C., and then at a secondtemperature of about 150° C. to 200 or 250° C., with the duration ofeach heating depending on the size, shape, and/or thickness of theintermediate. In another embodiment, the intermediate may be cured by aramped heating schedule, with the temperature ramped from ambienttemperature through a temperature of 70 to 150° C., and up to a final(oven) temperature of 250 or 300° C., at a change in heating rate of0.5° C. per minute, to 5° C. per minute. (See, e.g., U.S. Pat. No.4,785,075).

3. Three-Dimensional Objects.

As noted above, resins and methods as taught herein may be useful toform dual cure three-dimensional objects that are flame retardant. Insome embodiments, samples of the composition that are configured fortesting according to UL 94 have a thickness of 2 millimeters may achievea UL 94 V-0, V-1, or V-2 rating. For example, in some embodiments,samples of the composition configured for testing according to UL 94 andhaving a thickness of 2 millimeters may achieve a UL 94 V-0 rating.

Flammability tests may be performed following the procedure ofUnderwriter's Laboratory Bulletin 94 (“UL 94”), available atstandardscatalog.ul.com. Flame is applied in the vertical setup shown inFIG. 1 , and materials may be classified as V-0, V-1, or V-2, accordingto the criteria in Table 1. Sample Dimension: Length: 125 mm, Width: 15mm and three different thickness: 3 mm, 2 mm and 1.5 mm.

TABLE 1 UL 94 Procedure Flame height 20 mm Flame application time 2 × 10s The second flame application time beings as soon as the first burningtime ends Flammability rating UL 94 V Test criteria V-0 V-1 V-2 Burningtime of ≤10 ≤30 ≤30 each individual test specimen(s) (after first andsecond flame applications) Total burning ≤50 ≤250 ≤250 time(s) (10flaime applications) Burning and ≤30 ≤60 ≤60 afterglow times aftersecond flame application(s) Dripping of burning no no yes specimens(ignition of cotton batting) Cobustion up to no no no holding clamp(specimens completely burned)

Table 2 presents a summary of test procedures and requirements of thefour UL94 classifications (HB, V0, V1, V2):

TABLE 2 UL 94 Test Procedures Horizontal Test UL94 Vertical Test UL94Classification HB V0 V1 V2 Number of 3 3 5 5 5 specimen Thisckness of <3mm 3 to 13 up to max. 13 mm specimen mm 1^(st) flame 30 sec. 30 sec. 10sec. 10 sec. 10 sec. application 2^(nd) flame — — 10 sec. 10 sec. 10sec. application Burning rate max. 75 max. 40 — — — mm/min mm/minAfterflame — — max. 10 max. 30 max. 30 time after 1^(st) sec. sec. sec.flame application for each individual specimen Afterflame — — max. 30max. 60 max. 60 time after 2^(nd) sec. sec. sec. flame application foreach individual specimen Total — — max. 50 max. 250 max. 250 afterflametime sec. sec. sec. for all 5 specimen after 1^(st) and 2^(nd) flameapplication Afterflame or yes yes no no no afterglow of any specimen upto its end allowed Cotton — — no no yes indicator ignited by flamingparticles or drops allowed

Procedure: Apply flame for 10 sec, note the burn time. After extinguish,apply flame for another 10 sec, note the burn time. Total of these twotimes is used to determine the classification (e.g., V0/V1).

The present invention is explained in greater detail in the followingnon-limiting Examples.

Example A: By Chain Extension: Tetra Bromo Bisphenol A

Fifteen grams of a commercially available urethane acrylate (CN983), 5grams of commercially available acrylate monomer (CN2601), 29 grams of aBisphenol A diglycidyl ether resin with core-shell rubber modifiers(Kaneka MX153), 0.95 grams of 3,3′-diaminodiphenyl sulfone, 0.95 gramsof 4,4′-diaminodiphenyl sulfone, 21 grams of tetrabromobisphenol A(structure below), 6 grams of Nyacol APE 1540 (nonaqueous dispersion ofcolloidal antimony pentoxide), and 0.8 grams ofphenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed with 23grams of N,N′-dimethylacrylamide in a planetary centrifugal mixer toyield a homogeneous resin.

This resin was formed into a three-dimensional intermediate usingcontinuous liquid interface production (CLIP) on a Carbon Inc. M2printer (Carbon Inc., Redwood City, CA) operated in continuous exposuremode, using a 385 nm LED projector with a light intensity of 9 mW/cm² ata speed of 30 mm/hour. The formed material was cured in a convectionoven at temperatures up to 220° C. to yield the desired product. Themechanical properties of dual cured products produced from such resinswere evaluated by producing mechanical test samples in this manner, andare given in Table 3 below.

Example B1: By Brominated Epoxy: Diglycidyl Ether of BrominatedBisphenol A

Fifteen grams of a commercially available urethane acrylate (CN983), 5grams of commercially available acrylate monomer (CN2601), 26 grams of aBisphenol A diglycidyl ether resin with core-shell rubber modifiers(Kaneka MX153), 4.8 grams of 3,3′-diaminodiphenyl sulfone, 4.8 grams of4,4′-diaminodiphenyl sulfone, 22 grams of diglycidyl ether of brominatedbisphenol A (structure below), 5 grams of Nyacol APE 1540, and 0.8 gramsof phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed with 23grams of N,N′-dimethylacrylamide in a planetary centrifugal mixer toyield a homogeneous resin.

This resin was formed into a three-dimensional intermediate usingcontinuous liquid interface production (CLIP) in continuous exposuremode, using a 385 nm LED projector with a light intensity of 9 mW/cm² ata speed of 30 mm/hour. The formed material was cured in a convectionoven at temperatures up to 220° C. to yield the desired product. Themechanical properties of dual cured products produced from such resinswere evaluated by producing mechanical test samples in this manner, andare given in Table 3 below.

TABLE 3 Material Properties Example A Example B1 Tensile modulus (MPa)2800-3200 2800-3200 Tensile strength at break (MPa) 79.4 80.2 Elongationat break (%) 8.25 7 Glass transition temperature (E′, tanD) 119 C. 135C. Izod impact strength, notched (J/m) 34.2 41 Viscosity (cP) @25 C. 7451300 Flammability Test ( UL 94) −3 mm, V0 V0 2.5 mm

The UL 94 vertical flammability tests were done in accordance with thedescription in the specification provided above.

Notched Izod Impact Strength may be measured in accordance with ASTMD256.

Heat deflection temperature may be measured in accordance with ASTMD648.

Example B2: By Brominated Epoxy: Diglycidyl Ether of BrominatedBisphenol A and Brominated Oligomeric Epoxy

Twenty one grams of a commercially available urethane acrylate (CN983),22 grams of a Bisphenol A diglycidyl ether resin with core-shell rubbermodifiers (Kaneka MX153), 3.7 grams of 3,3′-diaminodiphenyl sulfone, 3.7grams of 4,4′-diaminodiphenyl sulfone, 8 grams of brominated bisphenol Aepoxy (diglycidyl ether of brominated bisphenol A, structure shownabove), 15 grams of brominated oligomeric epoxy (F-2016, brominatedpolybisphenol A epoxy, m.wt. 1600, structure shown below), 3 grams ofNyacol BurnEx ADP 494, 0.8 grams ofphenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 0.005% ofphenothiazine, 0.625% of 1,1-Bis(tert-amylperoxy)cyclohexane solution,and 0.37% of black pigment (Wikoff) were mixed with 22 grams ofN,N′-dimethylacrylamide in a planetary centrifugal mixer to yield ahomogeneous resin.

This resin was formed into a three-dimensional intermediate usingcontinuous liquid interface production (CLIP) in continuous exposuremode, using a 385 nm LED projector with a light intensity of 9 mW/cm2 ata speed of 30 mm/hour. The formed material was cured in a convectionoven at temperatures up to 220° C. to yield the desired product. Themechanical properties of dual cured products produced from such resinswere evaluated by producing mechanical test samples in this manner, andare given in Table 4 below.

TABLE 4 Material Properties Example B2 Tensile modulus (MPa) 3200-2500Tensile strength at break (MPa) 85-95 MPa Elongation at break (%)   7-8%Glass transition temperature (E′, tanD) 142 C. Izod impact strength,notched (J/m) 46 Viscosity (cP) @25 C. 1525 Flammability Test (UL 94) −3mm, V0 2.5 mm, 1.5 mm

Examples C and D: Non Reactive Brominated Flame Retardant

In the following examples, bromine was incorporated in the network usinga non reactive brominated oligomer. Mwt 15000, CAS 135229-48-0, F-3100(ICL Industrial Products)

Example C

Fifteen grams of a commercially available urethane acrylate (CN983), 5grams of commercially available acrylate monomer (CN2601), 28 grams of aBisphenol A diglycidyl ether resin with core-shell rubber modifiers(Kaneka MX153), 3.2 grams of 3,3′-diaminodiphenyl sulfone, 3.2 grams of4,4′-diaminodiphenyl sulfone, 23 grams of F-3100 (structure above), 6grams of Nyacol APE 1540, and 0.8 grams ofphenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed with 23grams of N,N′-dimethylacrylamide in a planetary centrifugal mixer toyield a homogeneous resin. This resin was formed into athree-dimensional intermediate using continuous liquid interfaceproduction (CLIP) in continuous exposure mode, using a 385 nm LEDprojector with a light intensity of 9 mW/cm² at a speed of 30 mm/hour.The formed material was cured in a convection oven at temperatures up to220° C. to yield the desired product. The mechanical properties of dualcured products produced from such resins were evaluated by producingmechanical test samples in this manner, and are given in Table 5 below.

Example D

Fifteen grams of a commercially available urethane acrylate (CN983), 5grams of commercially available acrylate monomer (CN2601), 28 grams of aBisphenol A diglycidyl ether resin with core-shell rubber modifiers(Kaneka MX153), 3.2 grams of 3,3′-diaminodiphenyl sulfone, 3.2 grams of4,4′-diaminodiphenyl sulfone, 12 grams of F-3100, 10 grams ofTetrabromobisphenol A, 6 grams of Nyacol APE 1540, and 0.8 grams ofphenylbis(2,4,6-trimethylbenzoyl)phosphine oxide were mixed with 23grams of N,N′-dimethylacrylamide in a planetary centrifugal mixer toyield a homogeneous resin. This resin was formed into athree-dimensional intermediate using continuous liquid interfaceproduction (CLIP) in continuous exposure mode, using a 385 nm LEDprojector with a light intensity of 9 mW/cm² at a speed of 30 mm/hour.The formed material was cured in a convection oven at temperatures up to220° C. to yield the desired product. The mechanical properties of dualcured products produced from such resins were evaluated by producingmechanical test samples in this manner, and are given in Table 5 below.

TABLE 5 Material Properties Example C Example D Tensile modulus (MPa)Tensile strength at break (MPa) Elongation at break (%) Glass transitiontemperature (E′, tanD) 120 C. Izod impact strength, notched (J/m) 34Viscosity (cP) @25 C. >100,000 62,500 Flammability Test ( UL 94) −3 mm,2.5 mm

The UL 94 vertical flammability tests are done in accordance with thedescription in the specification provided above.

Notched Izod Impact Strength may be measured in accordance with ASTMD256.

Heat deflection temperature may be measured in accordance with ASTMD648.

Examples E and F: Using Antimony Pentoxide Versus Antimony Trioxide

Antimony Pentoxide/Trioxide is used as a synergist in the brominatedformulations to improve the flame retardation efficiency. However, insome formulations, antimony pentoxide in a colloidal dispersion matrixmay be preferable as antimony pentoxide is smaller in particle size andhas higher particle stability in the formulation as compared to theantimony trioxide particles. Smaller particle size helps in lessscattering of the light, which aids in faster printing.

TABLE 6 Formulations with Antimony Pentoxide or Antimony TrioxideExample E Example F Components Weight % Weight % CN 983 15 15 CN 153(acrylated glycidyl 4.5 4.5 ether of Bisphenol A) DMAA 24.5 25(N,N′-dimethylacrylamide) TPO 0.8 0.8 (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) MX 153 26 27.5 TBBPA 16.5 16.5(tetrabromobisphenol A) 3,3′ DDS 3.2 3.5 (3,3′ diaminodiphenyl sulfone)Carbon Black 0.19 0.19 CN 2601 0 0 Nyacol APE 1540 5 0 Lanxess Antimony0 2 100.69 99.99 Amount of Antimony % 2 2 Bromine % 9.6954 9.696Viscosity, @25 C. in cps 1525 — Dc 16.241 8.076 Alpha 0.00608 0.0104Particle Stability- Centrifuge- No Complete 6000 rpm, 20 min, 9 accsettling settling

Example G: Using Antimony Pentoxide Functionalized with EthoxylatedAmine

In Examples E and F above, it was demonstrated that antimony pentoxideperforms better as compared to antimony trioxide in terms of particlestability and less scattering (lower alpha). In this experiment, twodifferent grades of antimony pentoxide were compared: Nyacol APE 1540:40% Antimony pentoxide dispersed in a polyester resin (colloidaldispersion); and BurnEx® ADP494: 74% Antimony pentoxide functionalizedwith ethoxylated amine (powder). Both of the Part B components of therespective formulations have the same antimony Pentoxide content at1.6%.

Part A: Components In % MX 153 27 F-2200HM 7 DMAA 8 TPO 0.8 Black 0.075F-2016 7 CN 2601 0 Total 49.875

Two different Part Bs: Components Part B-1 (in %) Part B-2(in %) 33 DDS3.3 3.3 44 DDS 3.3 3.3 DMAA 15 15 Genomer 4205 15 16.8 CN 2601 5 5Nyacol APE 4 — 1540 BurnEx ADP — 2.2 494 TBBPA 5 5 50.6 50.6

Upon mixing Part B (i.e., Part B-1 or Part B-2) with Part A in a 1:1ratio (by wt %) and measuring the Dc and Alpha as per CLIP process, theresin with B-2 had a lower alpha (less scattering), which aids in fasterprinting.

Part B-1 Part B-2 Dc 12.117 12.508 Alpha 0.00403 0.00360

Particle Stability: Formulations were tested on Lumifuge with 865 nm,profiles—1000, Interval—60 s, Speed—4000 rpm, Light Factor—1.0, Temp—25C. As reflected in the data presented in FIG. 2 , BurnEx® ADP494 PartB-2 is more stable as compared to the Nyacol APE 1540 Part B-1. Thislower instability index promotes a longer shelf life of the product.

The foregoing is illustrative of the present invention, and is not to beconstrued as limiting thereof. The invention is defined by the followingclaims, with equivalents of the claims to be included therein.

What is claimed is:
 1. A dual cure resin useful for making athree-dimensional object by stereolithography, comprising: (a)light-polymerizable monomers and/or prepolymers that can participate informing an intermediate object by stereolithography; (b)heat-polymerizable monomers and/or prepolymers; (c) a hardener, or achain extender; (d) a flame retardant synergist, said flame retardantsynergist comprising antimony pentoxide; and (e) optionally, an organicdiluent in a viscosity-reducing effective amount, wherein one or both ofsaid: (a) heat-polymerizable monomers and/or prepolymers, and said (c)hardener or chain extender, comprises a flame retardant group in itschemical structure, said flame retardant group comprising a halogengroup.
 2. The resin of claim 1, further comprising: (f) a toughener. 3.The resin of claim 1, wherein said hardener is present and comprises apolyamine, with said organic diluent included in an amount sufficient todissolve said hardener in said resin.
 4. The resin of claim 1, whereinsaid resin comprises both of said hardener and said chain extender. 5.The resin of claim 1, wherein said organic diluent is present andcomprises N,N′-dimethylacrylamide, n-vinyl-2-pyrrolidone, n-vinylformamide, n-vinyl caprolactam, acryloylmorpholine, or a mixture of twoor more thereof.
 6. The resin of claim 1, further comprising at leastone photoinitiator, optionally at least one dye, and optionally at leastone filler.
 7. The resin of claim 1, wherein said resin comprises acyanate ester or epoxy resin.
 8. The resin of claim 1, wherein saidheat-polymerizable monomers and/or prepolymers comprise an epoxy,optionally in combination with a cyanate ester resin.
 9. A method ofmaking a three-dimensional object, comprising: (a) providing the resinof claim 1; (b) producing by stereolithography a three-dimensionalintermediate from said dual cure resin, said intermediate having thesame shape as, or a shape to be imparted to, said three-dimensionalobject, said stereolithography including irradiating the resin withlight; (c) optionally washing said intermediate; and then (d) heatingsaid intermediate to a temperature at which said heat-polymerizablemonomers and/or prepolymers polymerize to produce said three-dimensionalobject.
 10. The method of claim 9, wherein said organic diluent ispresent and wherein said irradiating is carried out under conditions inwhich said organic diluent chemically reacts by an amount sufficient toincrease the strength of said intermediate.
 11. The method of claim 9,wherein said light-polymerizable monomers and/or prepolymers form asolid polymer scaffold during said producing step (b), which scaffolddegrades during said heating step (d) and forms a constituent necessaryfor the polymerization of said heat-polymerizable monomers and/orprepolymers.
 12. The method of claim 9, wherein said producing step (b)is carried out by bottom-up stereolithography.
 13. The method of claim9, wherein said producing step (b) is carried out by continuous liquidinterface production.
 14. The resin of claim 1, wherein said chainextender is present and wherein said resin further comprises a chainextender catalyst.
 15. The resin of claim 14, wherein said chainextender catalyst comprises an onium salt.
 16. The resin of claim 1,wherein the halogen group is bromine.
 17. The resin of claim 1, wherethe halogen group is present in an amount of from 1 to 20% by weight ofthe resin.
 18. The resin of claim 1, wherein the flame retardantsynergist is present in an amount of from 0.1 to 5% by weight of theresin.
 19. The resin of claim 1, wherein the hardener and the organicdiluent are present, and wherein the organic diluent solubilizes ordissolves said hardener in said resin.
 20. The resin of claim 1, whereinsaid antimony pentoxide is functionalized with ethoxylated amine.